SLIDES 


AT  THE 


PANAMA  CANAL 


By 


Major  General  GEORGE  W.  GOETHALS,  U.  S.  Army 
Governor  of  the  Panama  Canal 


Gift  of  the  Panama  CanalMmeum 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1916 


rl-J-  ■■>:--V-  -s:^. -jfV.aT  Jri-v'J 


SLIDES 

AT  THE 

PANAMA  CANAL. 


Extract  from  the  Annual  Report  of  Major  General  George 

W.  Goethals,  U.  S.  Army,  Governor  of  the  Panama  Canal, 

for  the  fiscal  year  ended  June  30, 1916. 


Although  the  question  of  the  sUdes  has  been  dealt  with  in  pre- 
vious annual  reports  and  official  documents,  there  continues  to  exist 
much  ignorance  on  the  subject.  Also  a  great  deal  has  been  written 
by  those  whose  little  knowledge  makes  them  dangerous,  and  to 
whose  statements  credence  is  given  because  of  the  position  or  prom- 
inence of  the  writers.  I  have  concluded,  therefore,  to  report  again 
on  the  situation,  even  at  the  expense  of  repetition,  notwithstand- 
ing the  general  belief  that  anything  pubhshed  in  annual  reports  is 
buried  in  obhvion.  Consideration  will  be  given  also  to  the  various 
theories  that  ^ave  been  advanced  and  to  the  remedies  that  have 
been  suggested. 

For  some  unaccountable  reason  there  seems  to  be  a  general  belief 
that  the  entire  length  of  the  Cut  is  affected.  A  report  emanating 
recently  from  English  sources  states  that  the  bottom  of  the  canal 
through  this  section  is  found  to  be  a  bog,  which  is  being  constantly 
pushed  up,  and  through  which  the  dredges  have  difficulty  in  main- 
taining a  channel;  further,  that  it  is  acknowledged  on  the  part  of 
those  in  charge  that  the  canal  is  a  failure,  and  that  American  engi- 
neers are  seeking  information  in  England  relative  to  the  Nicaragua 
route.  Such  reports  are  false,  and  there  is  no  foundation  for  them; 
yet  they  seem  to  have  gained  credence  probably  because  a  pending 
treaty  betw^een  the  United  States  and  Nicaragua  contemplates 
securing  from  the  latter  aU  rights  for  building  a  canal  on  its  territory. 
As  the  Nicaragua  route  was  at  one  time  the  one  most  generally 
favored  by  the  United  States,  investigations  by  commissions,  boards, 
and  commercial  bodies,  covering  a  series  of  years,  have  been  made 
of  the  route,  and  data  of  aU  kinds  collected;  consequently  every- 
thing that  is  known  about  that  route  can  be  found  at  home,  with- 
out the  necessity  of  seeking  information  in  England.  It  makes  a 
good  news  item,  however;  makes  converts  to  the  belief  that  the 


2  THE   PANAMA   CANAL. 

entire  8.75  miles  of  the  Cut  is  unstable,  liable  to  collapse  or  upheaval, 
completely  closing  the  canal  for  all  time,  is  useful  in  assisting  ship- 
ping companies  to  take  advantage  of  present  conditions  to  charter 
ships  at  excessive  rates  instead  of  complying  with  their  obligations, 
and  permits  an  increase  in  insurance  rates. 

Gaillard  Cut  extends  from  Pedro  Miguel  to  Gamboa,  a  distance  of 
8.75  miles.  The  canal  prism  through  this  section  averages  300  feet 
bottom  width,  and  has  a  depth  of  45  feet.  Every  foot  of  the  exist- 
ing channel  was  excavated  through  rock,  all  of  which,  though  of 
various  kinds  and  densities,  had  to  be  drilled  and  blasted  in  order 
to  remove  it.  It  is  possible  that  the  water  may  have  softened  some 
of  the  material,  yet  it  is  known  that  the  softer  varieties  of  rock 
encountered  in  the  excavation  were  protected  from  disintegration 
by  contact  with  water.  The  bog  theory  is  a  myth.  The  Cut  has 
been  stable  with  the  exceptions  of  the  portions  in  the  vicinity  of 
Culebra  and  at  Cucaracha.  The  slides  at  Culebra  are  on  both  sides 
of  the  waterway,  occupying  a  length  of  2,800  feet,  while  the  channel 
affected  by  the  Cucaracha  slide  is  less  than  2,000  feet  long,  so  that 
out  of  a  total  length  of  8.75  miles  only  0.88  mile  is  affected. 

Another  misconception  that  exists  relates  to  the  character  of  the 
slides.  They  have  not  been,  except  in  part  at  Cucaracha,  a  slipping 
down  of  portions  of  a  bank  in  order  to  reach  the  slope  at  which  the 
material  will  stand.  Slides  of  this  character  have  occurred,  but 
they  were  small  in  extent  and  easily  handled.  Those  at  Culebra 
are  breaks  resulting  from  deformation  or  crushing  of  underlying 
strata  which,  under  changed  conditions,  could  not  bear  the  weight 
of  the  superimposed  mass,  and  caused  a  vertical  settlement  or  drop 
of  the  overlying  material,  which  subsequently  moved  into  the 
prism.  Final  rest  will  be  secured  when  all  the  material  that  is  in 
motion  has  been  removed.  As  is  shown  by  experience  with  smaller 
breaks  that  have  occurred  from  the  same  cause,  when  the  end  is 
reached  the  final  surface  will  be  concave,  or  bowl  shaped. 

When  water  was  turned  into  the  Cut  on  October  10,  1913,  the 
channel  was  completed  to  full  width  and  depth  except  at  Cucaracha, 
where  the  steam  shovels  were  making  but  little  headway  against 
the  slide;  three  benches  which  had  been  left  (one  at  La  Pita  Point, 
one  on  the  east  side  near  Empire,  and  one  on  the  west  side  oppo- 
site Cucaracha) ;  the  inclines,  one  at  either  end  of  the  Cut ;  and  the 
remains  of  two  small  slides,  one  on  the  east  side,  of  the  ''break" 
variety,  and  the  other  on  the  west  side,  a  typical  slide  of  clay  which 
occurred  prior  to  the  removal  of  the  steam  shovels,  both  of  which, 
between  Empire  and  Culebra,  were  cleaned  up  by  the  dredges  and 
have  remained  quiescent  since. 

Cucaracha  slide  is  on  the  east  side  of  the  canal  south  of  Gold  Hill. 
It  began  to  give  trouble  as  early  as  1884,  during  the  operations  of 


REPORT  OF   THE   GOVERNOR.  3 

the  French  Canal  Co.,  but  all  the  indications  pointed  to  a  surface 
movement  only.  The  French  built  an  elaborate  system  of  drainage 
to  overcome  the  difficulty,  and,  while  successful  so  long  as  work  of 
excavation  was  suspended,  further  deepening  of  the  Cut  in  the  vicin- 
ity resulted  in  renewed  activity,  with  complete  destruction  of  the 
drainage  system;  the  remaining  part  of  this  system  was  carried 
away  by  the  slide  in  1907.  The  slide  gave  trouble  in  1906,  when 
excavation  proceeded  through  this  section.  The  difficulties  increased 
as  the  depth  increased  and  in  the  autumn  of  1907  became  most  for- 
midable. From  this  time  until  1910  the  difficulties  became  less,  and 
it  was  believed  that  they  had  been  overcome  and  that  the  clay  re- 
maining would  be  supported  by  a  rock  dike  which  was  uncovered 
and  which  apparently  possessed  ample  strength  to  retain  the  mass 
above  and  back  of  it.  On  January  20,  1913,  the  rock  dike  broke  at 
or  below  the  bottom  level  of  the  canal  and  completely  filled  the 
prism  mth  clay  and  rock  for  a  length  of  1,600  feet,  to  a  depth  of  30 
feet  on  the  bank  opposite  from  the  slide,  increasing  toward  the  east 
on  a  slope  of  about  1  on  4.  Steps  were  taken,  by  means  of  sluicing, 
to  wash  back  as  much  of  the  top  portions  of  the  clay  as  possible  into 
the  valley  on  the  east  side  of  the  ridge.  As  steam  shovels  could  not 
cope  with  the  situation  economically  and  advantageously  and  as  the 
remainder  of  the  Cut  was  ready  for  the  admission  of  water,  this  was 
allowed  to  enter  and  recourse  had  to  dredges  for  the  removal  of  the 
balance.  The  time  within  which  a  passage  through  the  slide  was 
cut,  as  well  as  the  cost,  is  conclusive  that  this  method  was  the  most 
efficient  and  economical  way  of  handling  the  material. 

In  July,  1914,  troubles  in  Mexico  interfered  with  the  handling  of 
cargoes  by  the  Tehauntepec  route,  and  shipping  interests  were 
clamoring  for  relief.  The  dredges  had  secured  a  channel  through  the 
slide,  and  the  Panama  Railroad  operated  a  line  of  barges  through 
the  canal  between  the  terminal  ports,  but  these  could  not  handle 
the  traffic.  While  the  full  depth  and  width  had  not  been  secured 
through  the  slide,  the  channel  was  sufficient  for  the  passage  of  ship- 
ping, and  consequently  the  canal  was  opened  to  commerce  in  August, 
1914. 

Several  movements  have  occurred  since  at  Cucaracha,  but  they 
were  handled  easily  and  did  not  delay  commerce  until  the  last  of 
August,  1916,  when  a  movement  occurred,  bringing  down  material 
from  the  northeast  corner  of  the  slide  area,  and  moved  huge  rock 
bowlders  across  the  center  line  of  the  channel,  so  constricting  it  as 
to  force  a  suspension  of  navigation  on  August  30,  1916.  The  larg- 
est mass  of  rock  occupied  a  length  of  65  feet.  The  bowlders  required 
drilling  and  blasting  operations  in  order  to  remove  them.  Holes  20 
feet  deep  in  a  ffintlike  substance  were  drilled  at  great  expense  of 
time  and  drills  before  they  could  be  broken  up  sufficiently  for  the 


4  THE   PANAMA  CANAL. 

dredges  to  handle,  and  the  closure  of  the  canal  lasted  eight  days, 
although  two  small  ships  were  passed  through  in  the  interval. 

Gold  Hill  is  of  basalt,  thrown  up  in  a  molten  state  through  the 
sedimentary  deposits  that  already  existed  and  poured  over  the 
deposits  on  either  side  of  the  stem,  giving  to  the  vertical  section  the 
general  shape  of  a  mushroom.  The  portions  projecting  beyond  the 
stem,  being  left  unsupported,  broke  when  the  material  moved  from 
under,  and  the  rock  thus  detached  came  down  with  the  rest  of  the 
material  at  Cucaracha,  This  same  action  occurred  on  the  opposite' 
side  of  Gold  Hill  within  a  few  months  after  the  east  Culebra  slide 
became  active. 

A  slide  developed  during  the  excavation  in  1906  north  of  Gold 
Hill  on  the  east  side  of  the  Cut.  This  was  a  typical  slide,  a  surface 
movement  which  flattens  the  slope,  and  slides  of  this  character  had 
occurred  in  this  locality  during  the  French  occupancy.  The  French 
endeavored  to  overcome  them  by  drainage  tunnels,  but  the  mate- 
rial through  which  they  were  built  was  too  fine  grained  to  permit 
the  free  passage  of  water,  and  the  method  was  not  continued. 

In  1907,  at  the  village  of  Culebra,  the  type  of  slides  designated 
"breaks"  first  manifested  itself.  When  the  excavation  had  reached 
a  depth  of  135  feet  above  the  finished  bottom  level,  a  crack  appeared 
in  the  surface  of  the  undisturbed  ground,  extending  from  one  point 
on  the  prism  slope  to  another.  Subsequently  there  was  a  subsidence 
of  the  surface  on  the  side  of  the  crack  farthest  from  the  prism,  accom- 
panied by  an  upward  movement  of  a  portion  of  the  bottom  of  the 
excavated  area  a  little  distance  from  the  foot  of  the  slope.  This 
was  followed  later  by  a  settlement  of  the  mass  between  the  crack 
and  the  Cut,  which  ultimately  slid  into  the  prism.  The  first  break 
affected  but  a  few  hundred  feet,  but  as  the  depth  of  excavation 
increased  the  breaks  became  more  extensive  both  in  length  and 
quantities  of  material  involved;  then  they  occurred  on  both  the 
east  and  west  banks,  the  upward  movement  along  the  bottom  of 
the  excavation  continuing  until  the  area  affected  extended  for  a 
length  of  2,000  feet  north  of  Gold  Hill.  The  borings  of  record  failed 
to  disclose  any  weak  underlying  strata. 

The  cause  undoubtedly  was  the  unequal  distribution  of  the  pres- 
sure exerted  by  the  adjacent  banks.  Such  being  the  case,  it  fol- 
lowed that  if  the  height  of  these  banks  were  reduced  the  movement 
would  be  lessened,  and  if  reduced  sufficiently  would  cease  entirely. 
Subsequent  events  proved  this  to  be  correct.  The  banks  were  light- 
ened by  taking  material  from  the  top,  and  there  resulted  final  slopes 
through  this  portion  of  the  Cut  of  1  on  1^  to  1  on  6^  for  the  east  side 
and  from  1  on  2.46  to  1  on  4.35  for  the  west  side;  the  slopes  con- 
sisted of  a  series  of  steps.     The  upheaving  of  the  bottom  ceased 


REPORT  OF    THE   GOVERNOR.  5 

entirely,  as  already  noted,  and  the  canal  prism  was  carried  to  full 
depth  and  width  throughout  the  entire  2,000  feet. 

Toward  the  close  of  the  dry  season,  in  April,  1913,  a  crack  ap- 
peared on  the  east  side  opposite  Culebra,  about  1,300  feet  from  the 
prism,  in  an  old  French  dump.  It  was  parallel  to  the  canal,  did 
not  join  the  banks,  there  was  no  breaking  up  of  the  banks  between 
it  and  the  Cut,  nor  any  subsidence — in  short,  there  were  none  of  the 
indications  that  accompanied  previous  breaks.  The  geologist  be- 
lieved that  it  was  due  to  the  deformation  of  the  underlying  strata 
and  advocated  lightening  the  banks  by  sluicing  and  steam  shovels, 
which  was  done.  While  this  work  was  in  progress  the  crack  gradu- 
ally closed,  and  though  the  surface  between  the  crack  and  the  Cut 
was  in  places  noticeably  below  the  level  of  the  surface  to  the  east 
of  the  crack,  the  closure  was  construed  to  mean  that  a  condition  of 
equilibrium  had  been  reached.  The  canal  through  this  section  was 
completed,  the  water  was  turned  in,  and  no  further  trouble  was 
anticipated  in  this  section. 

A  crack  had  existed  for  some  years  at  the  foot  of  Zion  Hill,  south- 
east of  Culebra.  The  hill  was  pronounced  geologically  secure  against 
any  movement,  and  when  the  material  was  dug  away  from  the 
upper  portions  of  this  bank,  and  the  slopes  of  the  final  bench  reached 
the  crack,  it  did  not  increase  and  there  was  no  movement. 

Just  prior  to  turning  in  the  water  a  rock  slide  occurred  north  of 
Gold  Hill  on  the  east  side,  increasing  somewhat  with  the  admission 
of  water,  causing  no  change,  however,  in  the  crack  on  the  top.  A 
similar  slide  occurred  on  the  west  side  after  the  prism  filled  with 
water.  In  both  instances  the  movements  were  typical  of  the  ordinary 
slides — an  adjustment  of  the  slopes.  The  material  was  easily  han- 
dled by  the  dredges  and  the  channel  freed  of  all  obstructions  before 
the  canal  was  opened  to  navigation.  This  condition  continued  until 
October  14,  1914,  when,  without  any  warning,  a  section  of  the  east 
bank  north  of  Gold  Hill  settled  vertically  20  feet.  This  section 
measured  2,000  feet  along  the  prism  face,  and  extended  back  about 
1,000  feet  from  the  axis  of  the  canal,  generally  along  an  irregular 
curved  line,  but  did  not  extend  back  to  include  the  crack  that  had 
developed  in  1913.  The  top  of  the  bank  was  from  300  to  350  feet 
above  sea  level.  After  the  settlement  the  upper  surface  of  the 
portion  that  broke  away  remained  practically  parallel  to  its  original 
position,  and  the  existing  benches  of  the  upper  part  of  the  slide  had 
not  changed  their  relative  positions,  though  they  were  badly  broken 
up,  but  the  lower  strata  were  squeezed  out  across  the  canal,  reducing 
the  depth  of  water  from  45  feet  to  9  inches  at  one  point  within  an 
hour's  time.  Subsequently  the  broken  mass  moved  into  the  Cut,  as 
was  the  case  with  other  breaks.  Navigation  was  suspended  for  a 
week,  but  after  this  and  until  August,  1915,  the  dredges  were  able  for 


6  THE  PANAIMA  CANAL. 

the  most  part  to  keep  up  with  the  material  as  it  came  down,  and 
would  have  been  able  to  maintain  such  condition  had  not  a  movement 
occurred  on  the  west  bank,  necessitating  work  on  this  side  to  the 
detriment  of  the  east  side. 

A  crack  was  foimd  on  the  slope  of  Zion  Hill  in  Jmie,  1914,  higher 
up  than  the  crack  already  mentioned,  but  observations  made  upon 
it  showed  no  movement,  and  the  solidity  of  the  hill  was  never 
doubted.  Subsequent  to  the  break  on  the  east  side,  a  gradual  but 
general  breaking  up  of  the  west  bank  followed.  The  crack  on  the 
slope  increased  in  size  and  new  ones  developed  farther  up  the  hill^ 
imtil  finally  one  extended  to  elevation  480  above  sea  level,  the  limit 
of  the  present  break.  The  movement  into  the  Cut  from  the  west 
bank  occurred  early  in  August,  1915,  when  a  section  of  Zion  Hill 
broke  away  and  settled  down.  The  edge  of  the  break  on  this  side  is 
also  a  curve. 

The  movements  from  the  two  sides  were  toward  the  central  portion 
of  the  inclosed  area,  and  at  this  central  portion  the  bottom  was 
forced  up,  at  first  forming  an  island,  then  a  peninsula  projecting  from 
the  east  bank,  and  finally  an  isthmus  entirely  across  the  channel. 
The  barrier  increased  until  it  had  a  length  of  255  feet  along  the  axis 
of  the  canal  and  an  elevation  of  65  feet  above  the  surface  of  the 
water.  Tlie  movements  on  the  two  sides  are  entirely  different  in 
character.  On  the  east  side  a  settlement  of  a  mass  occurs,  the  top 
generally  tilting  backward  from  the  prism,  with  a  shoving  out  below. 
On  the  west  side,  for  the  most  part,  rock  masses  become  detached  and 
gradually  settle  down  vertically,  with  very  little  lateral  movement^ 
pushing  out  the  material  along  the  prism  face. 

When  the  break  occurred  on  the  east  side  it  was  realized  that  it 
would  extend  eventually  back  to  the  limiting  cracks,  and  that  all  the 
material  lying  above  some  surface,  concave  in  shape,  unless  removed, 
would  eventually  enter  the  prism.  It  was  impossible  to  handle  any 
of  it  by  hydraulics  away  from  the  Cut,  and  the  only  other  method 
would  be  by  steam  shovels.  These  could  only  operate  on  firm 
ground,  and  would  necessitate  the  establishment  of  dimips.  The 
number  of  shovels  that  could  be  worked  would  be  limited,  and  con- 
siderable excavation  would  be  required  before  the  sliding  material 
could  be  attacked.  The  dredges  were  capable  of  and  were  removing 
over  1,000,000  cubic  yards  per  month  without  any  of  the  difficulties 
attending  steam-shovel  operations,  and  what  could  be  accomplished 
by  the  latter  would  be  relatively  so  small  and  the  cost  so  high  that 
the  idea  of  introducing  steam  shovels  was  abandoned  and  the  decision 
reached  that  the  material  must  be  removed  from  the  canal  side  by  the 
dredges. 

From  experience  with  other  breaks,  it  was  known  that  the  move- 
ment would  not  be   continuous.     A  settlement  occurs,  by  which 


REPORT   OF    THE   GOVERNOR.  7 

material  is  pushed  into  the  prism ;  the  movement  is  at  first  heavy  and 
rapid,  gradually  diminishes,  and  finally  ceases.  This  condition  of  rest 
is  distm'bed  either  by  the  rains  or  by  the  operations  of  the  dredges 
cutting  into  the  banks.  As  all  the  material  liable  to  move  must  be 
taken  out  by  the  dredges  from  the  Cut,  there  would  come  a  time 
when  the  machines  would  be  idle,  waiting  for  a  movement  to  give 
additional  material  for  them  to  handle.  The  judicious  application 
of  hydraulicking  the  bank  would  avoid  such  a  condition,  conse- 
quently pumps  for  sluicing  operations  were  installed  on  two  barges. 
These  have  been  used  for  cutting  and  maintaining  surface  drainage 
and  for  washing  down  material  to  the  dredges,  when  the  conditions 
warranted  it. 

The  finished  section  from  Gold  Hill  north  left  an  enormous  mass  of 
hard  rock  on  the  east  side  and  at  the  northwest  corner  of  Gold  Hill. 
When  the  break  occurred  in  1914  this  mass  of  rock  was  moved  slowly 
into  the  prism,  but  finally  came  to  rest  and  seemed  to  hold  the 
material  back  of  it,  limiting  the  area  of  interference  in  the  channel. 
It  stood  up  boldly 'for  nearly  100  feet  and  was  designated  by  the 
working  force  as  ''Gibraltar/'  which  designation  will  be  used  when 
referring  to  this  mass  of  rock. 

The  slipping  of  the  material  into  the  Cut  removed  the  support  to 
the  mushroom  portions  of  Gold  HiU  on  its  north  side,  which  broke  off 
in  large  masses  and  followed  down  diagonally  toward  the  prism,  the 
effect  being  similar  to  that  described  as  having  taken  place  at 
Cucaracha,  and  the  direction  of  the  movement  was  due,  no  doubt,  to 
the  retaining  effect  of  "Gibraltar,"  though  this  took  up  slow  move- 
ments at  times  when  the  heavier  masses  back  of  it  were  disturbed  by 
subsequent  settlements. 

If  the  width  of  the  prism  through  the  slide  section  remained  as 
fixed  for  the  project — 300  feet  bottom  width — every  movement  that 
occurred  on  either  the  east  or  west  bank  would  contract  the  channel, 
and  should  a  movement  occur  in  both  banks  at  the  same  time  it 
would  probably  result  in  closing  the  canal  to  navigation.  The  neces- 
sity of  restoring  the  channel  to  permit  the  passage  of  ships  and  the 
maintenaaice  of  navigation  were  the  main  considerations.  An  addi- 
tion to  the  width  sufficient  to  take  care  of  material  pushed  in  by 
subsequent  movements,  thereby  increasing  the  chances  of  main- 
taining a  channel,  was  considered  advisable  until  all  the  loosened 
material  had  been  removed.  This  led  to  a  modification  of  the  pro- 
jected width,  which  was  increased  to  500  feet,  100  feet  on  either  side 
of  the  original  prism  lines. 

The  conditions  as  they  existed  then — in  November,  1915 — ^found 
the  canal  closed  to  navigation  indefinitely.  There  was  across  it  an 
isthmus  250  feet  long  in  the  direction  of  the  axis  of  the  canal,  the  top 
of  which  was  about  65  feet  above  water;  the  dredging  operations 


8  THE   PANAMA   CANAL. 

were  confined  to  the  north  of  this  isthmus,  working  toward  the  south, 
with  arrangements  made  for  washing  down  the  material  in  case  it  was 
advisable  to  accelerate  the  motion  of  aiiy  part  of  the  sliding  area, 
and  with  the  project  modified  so  as  to  give  a  completed  width  north 
of  Gold  Hill  of  500  feet. 

In  Occober,  1915,  the  President  of  tlie  United  States  was  advised 
by  a  member  of  the  National  Academy  of  Sciences — which  was 
organized  by  an  act  of  Congress  to  give  expert  advice  to  the  President 
and  Congress  on  scientific  matters — who  stated  that  one  of  its  mem- 
bers had  made  an  extensive  study  of  earth  slides  in  tropical  countries, 
and  was  convinced  that  there  were  relatively  simple  ways  by  which 
they  could  be  stopped,  and  suggested  that  a  committee  of  mining 
engineers  and  geologists  of  the  academy  be  appointed  to  consider  his 
propositions.  In  consequence  of  this,  the  President  of  the  United 
States  requested  that  a  committee  be  appointed  by  the  National 
Academy  of  Sciences  to  '^  Consider  and  report  upon  the  possibility 
of  controUing  the  slides,  which  are  seriously  interfering  with  the  use 
of  The  Panama  Canal."  From  the  correspondence  it  appears  that 
at  a  meeting  held  in  New  York,  "*  *  *  the  hope  was  repeatedly 
expressed  that  an  effective  solution  may  speedily  be  found." 

The  coming  of  the  committee  was  welcomed  on  the  Isthmus,  for 
so  much  misinformation  had  been  sent  broadcast,  doing  more  injury 
to  the  canal  than  the  closing  of  it  by  the  slides;  confidence  had  been 
upset ;  and  io  was  hoped  not  only  that  a  remedy  would  be  forthcoming 
but  that  the  report  of  the  committee  would  be  able  to  restore  con- 
fidence in  the  project,  especially  as  those  connected  with  the  work 
knew  that  the  methods  adopted  would  overcome  the  difficulties  for 
good  and  all,  given  the  time  and  money,  and  that  the  waterway  would 
be  all  that  had  been  expected. 

Probably  the  greatest  injury  done  the  canal  was  through  Prof. 
Benjamin  Le  Roy  Miller,  Ph.  D.,  who  occupies  the  chair  of  geology 
at  Lehigh  University.  On  returning  to  New  York  from  Costa  Rica 
he  stayed  here  a  couple  of  days  awaiting  a  steamer.  He  was  given 
every  facility  to  examine  the  slides  at  Culebra,  which  were  then  at 
their  worst,  and  he  is  reported  to  have  said  for  publication  on  his 
arrival  in  the  United  States  that  he  had  made  a  "  thorough  examina- 
tion of  the  slides,"  and  the  conditions  found  were  as  follows — the 
statement  appearing  in  quotation  marks  in  the  press  item: 

At  the  Culebra  Cut  *  *  *  cracks  have  formed  over  1,300  feet  back  from  the 
canal,  and  all  of  the  ground  intervening  is  moving  toward  the  Cut.  There  is  no  doubt 
that  much  rock,  now  apparently  stable,  also  will  move,  as  its  support  is  withdrawn  by 
the  removal  of  loose  earth  and  rock.  Before  the  canal  can  be  said  to  be  completed 
and  permanently  opened  to  traffic,  the  amount  of  material  that  must  be  taken  out 
will  not  fall  far  short  of  the  amount  already  taken  from  the  Culebra  Cut. 

Transportation  companies  planning  to  use  the  canal  should  realize  that  they  must 
not  expect  uninterrupted  service  for  several  years.    During  the  dry  season  the  canal 


REPORT   OF    THE   GOVERNOR.  9 

may  be  opened,  but  it  is  certain  to  be  closed  during  the  rainy  season  when  the  earth 
is  soaked  with  water  and  its  movement  toward  the  canal  facilitated. 

In  view  of  the  extent  of  the  material  that  has  now  started  toward  the  Cut,  it  seems 
that  steam  shovels  should  again  be  employed.  Practically  all  of  Gold  Hill  and  much 
of  Zion  Hill  must  be  removed,  and  to  wait  until  the  earth  breaks  loose  and  enters  the 
Cut  where  the  dredges  can  attack  it  seems  unwise,  and  unquestionably  longer  delays 
the  completion  of  the  project.  If  dredges  alone  are  employed,  as  at  present,  the  canal 
may  be  kept  clear  during  the  months  when  rainfall  is  lightened,  but  for  many  years 
to  come  the  rainy  season  is  almost  certain  to  cause  such  slides  as  to  close  the  canal 
for  weeks  or  even  months. 

The  "thorough  exammation "  occupied  fully  three  or  four  hours  of 
his  time.  The  position  that  he  occupied  in  one  of  the  leading  uni- 
versities of  the  United  States  gave  credence  to  his  statements,  which 
were  copied  broadcast,  and  commented  upon  editorially  to  the  detri- 
ment of  the  canal.  His  dire  predictions  were  naturally  unsettling  to 
shipping  interests,  which  were  guided  by  them  to  some  extent  in 
routing  their  commerce  elsewhere. 

It  was  anticipated  that  the  committee  from  the  National  Academy 
of  Sciences  would  make  a  more  thorough  examination  than  Prof. 
Miller  had  done,  and  it  was  hoped  that,  as  a  result,  the  statements 
of  Prof.  Benjamin  Le  Roy  Miller,  Ph.  D.,  would  be  found  to  be  what 
we  considered  them — erroneous,  unwarranted,  and  unfair,  and  help 
restore  the  confidence  that  he  had  helped  to  destroy. 

The  preliminary  report  by  the  committee  of  the  National  Academy 
of  Sciences  was  submitted  to  the  President  in  January,  1916.  At 
that  time  they  expected  that  their  final  report  would  be  completed 
in  April,  but  up  to  date  it  has  not  been  received.  The  preliminary 
report  will  be  found  in  Appendix  N.  It  will  be  noted  that  the  state- 
ment made  by  Prof.  Miller,  that  practically  all  Gold  Hill  and  much  of 
Zion  HiU  must  be  removed,  is  not  concurred  in;  and  in  this  connection 
it  should  be  remembered  that  a  committee  of  this  character  expresses 
its  opinions  guardedly,  for  whatever  happens  they  must  be  found  on 
the  right  side.  They  advocated,  as  a  matter  of  scientific  interest, 
the  making  of  an  accurate  triangulat,ion  of  the  hiils  in  question — 
Gold,  Contractors,  Culebra,  and  Zion — which  has  been  done.  By 
checks  made  at  frequent  intervals  the  slightest  movement  on  the 
part  of  any  of  the  four  hiUs  would  be  disclosed  at  once.  No  movement 
of  any  kind  has  taken  place. 

The  committee  expressed  the  belief  that  every  available  and  prac- 
ticable device  for  controlling  the  water,  both  on  the  surface  and  under- 
ground should  be  employed,  and  to  this  end  advocated  covermg  the 
slopes  with  vegetation  to  prevent  surface  wash,  closing  peripheral 
cracks,  draining  undisturbed  and  threatened  areas,  and  draining  by 
tunnels. 

For  several  years  the  expedient  of  covering  the  slopes  with  vegeta- 
tion has  been  carried  on,  starting  under  the  direction  of  Dr.  Pittier, 
of  the  Smithsonian  Institution.     Where  the  surface  of  the  ground  is 


10  THE   PANAMA  CANAL. 

in  motion,  as  in  the  case  of  active  slides,  the  roots  are  disturbed,  and 
the  steady  growth  of  vegetation  is  impracticable.  Trees  and  vege- 
tation of  all  kinds  growing  on  the  surface  of  the  ground  which  broke 
in  October,  1914,  were  carried  down  the  shde  and  exercised  no 
deterrmg  effect  whatsoever.  On  shding  ground  there  is  not  sufficient 
time  to  plant  anything  and  no  good  would  be  accomplished.  Where 
the  banks  consist  of  the  red  clay  of  the  country,  it  is  only  after  con- 
siderable difficulty  that  grass  of  any  kind  can  be  grown  on  them. 
Vegetation  stops  erosion;  on  this  account  the  work  was  undertaken 
and  is  bemg  carried  on. 

When  peripheral  cracks  occur  in  rock  with  sufficient  earth  covering 
they  may  be  effectually  closed  by  the  use  of  a  hydraulic  grader,  as 
was  done  in  an  incipient  slide  on  the  west  bank  of  the  canal  near 
Las  Cascadas,  The  sluicing  down  of  the  earth  into  a  uniform  slope 
not  only  fills  the  cracks  and  prevents  the  access  of  surface  water  into 
them,  but  facilitates  the  drainage  by  providing  a  ready  means  of 
run-off  into  the  canal.  This  method,  while  apphed  with  good  results 
at  the  north  end  of  the  East  Culebra  slide,  so  long  as  the  material  is 
at  rest,  a  subsequent  movement  develops  new  cracks  and  irregu- 
larities so  that  until  all  loose  clay  and  rock  is  removed  and  the  final 
slope  reached,  the  relief  is  temporary  only.  Where  there  is  very 
little  earth  covering,  as  is  the  case  on  Culebra  HiU,  and  where  the 
cracks  are  wide  and  extend  a  great  depth  in  rock,  it  is  not  practicable 
to  close  them  permanently  without  expense  that  is  disproportionate 
to  the  results  obtained. 

In  compliance  with  the  expressed  wishes  of  the  committee  while 
on  the  Isthmus;  subsurface  tile  drains  have  been  installed  within  an 
area  on  Culebra  Hill  as  an  experiment.  Also,  as  suggested  by  the 
committee,  the  fault  fissure  under  the  hard  Obispo  tuff  on  the  north 
side  of  Contractors  Hill  has  been  sealed  and  a  concrete-lined  drain 
constructed,  draining  the  surface  water  into  the  canal,  with  a  view 
to  the  protection  of  the  Cucaracha  rock  beds  adjacent  to  this  portion 
of  Contractors  HiU. 

It  is  admitted  that  if  the  water  could  be  entirely  excluded  the 
earth  movements  would  cease,  but  unfortunately  this  is  impossible. 
With  the  heavy  tropical  downpours  the  best  that  can  be  done  is  by 
drainage,  to  carry  away  what  falls  as  rapidly  as  possible,  but  ground 
water  can  not  be  eliminated.  So  far  as  concerns  ground  water,  the 
construction  of  the  canal  has  created  entirely  new  conditions.  The 
old  tributaries  of  the  Chagres  River  and  those  of  the  Rio  Grande, 
which  formerly  were  natural'  drains,  are  now  well  above  the  water 
surface  of  the  canal,  and  the  canal  has  become  the  drainage  channel 
for  the  countr}^  for  miles  on  either  side.  Even  assuming  that  were  it 
possible  to  devise  a  system  for  getting  rid  of  ground  water,  it  must  still 
exist  below  the  surface  of  the  water  in  the  canal  itself.     The  slides 


REPORT  OF   THE   GOVERNOR.  H 

in  question  affect  the  banks  for  a  considerable  distance  down,  prob- 
ably below  the  bottom  of  the  canal,  and  if  ground  water  be  primarily 
the  cause,  then  it  can  not  be  removed  from  the  strata  at  which  the 
trouble  starts. 

Surface  drainage  was  maintained  throughout  the  period  of  dry 
excavation.  The  adjacent  country  on  either  side  of  the  canal  was 
drained  through  the  east  and  west  diversions,  which  continued  to 
act  as  drains,  discharging  their  accumulated  waters  into  the  Chagres. 
In  relieving  the  pressure,  force  pumps  on  barges  have  enabled  the 
washing  down  of  part  of  the  material,  as  already  explained.  The 
hydraulic  grader  which  was  constructed  in  July,  1914,  and  put  in 
commission  in  August,  1914,  was  built  especially  for  opening  chan- 
nels to  expedite  surface  drainage  at  various  points  along  the  line  of 
the  canal,  and  to  maintain  them,  and  this  work  has  been  carried  on, 
although  suspended  south  of  the  slide,  due  to  the  interruption  and 
shut-off  of  the  channel  last  fall  and  winter. 

So  long  as  the  slides  are  active  and  the  configurations  of  their  sur- 
faces change  as  rapidly  as  they  now  do,  it  is  impracticable  to  open 
and  maintain  the  permanent  drains  recommended  in  the  moving 
areas.  When  equilibrium  is  restored,  and  as  a  means  of  promoting 
permanent  stability,  the  drains  of  a  permanent  character  should  be 
constructed  and  maintained. 

Drainage  by  tunnels  has  been  considered  in  connection  with  data 
obtained  since  the  committee's  report  was  written,  as  the  result  of 
experiments  suggested  by  the  chairman  of  the  committee.  Dr.  Van 
Hise,  through  whom  the  services  of  Prof.  Warren  J.  Mead,  of  the 
University  of  Wisconsin,  were  secured,  and  who  was  assisted  by 
Mr.  Donald  F.  IMacDonald  in  making  tests  of  the  rock  formation  in 
which  the  east  and  west  Culebra  and  Cucaracha  slides  have  occurred. 
I  have  received  from  Mr.  MacDonald,  the  geologist,  a  brief  report, 
hereto  appended,  marked  ''Appendix  O,"  which  states  the  result  of 
the  experiments,  as  follows: 

Twenty-one  average  samples  of  the  Cucaraclia  or  sliding  formation  were  taken 
from  below  the  water  level  of  the  canal.  These  samples,  completely  saturated,  con- 
tained 12.20  per  cent  of  water  by  weight,  or  27.8  per  cent  by  volume.  The  16  average 
samples  taken  from  well  above  the  level  of  ground  water,  where  the  rocks  were  much 
jointed  and  fractured  and,  therefore,  perfectly  drained,  contained  10.60  per  cent  of 
water  by  weight.  As  shown  above,  12.2  per  cent  of  water  by  weight  fills  all  of  the  pore 
spaces  of  the  rock;  therefore,  10.6  per  cent  by  weight  fills  only  87  per  cent  of  them, 
leaving  13  per  cent  of  the  total  pore  space  as  having  been  emptied  by  drainage  and  by 
drying.  Now,  13  pei*  cent  of  27.8  per  cent  is  3.6  per  cent  of  the  total  volume  of  the 
rock.  This  shows  that  natural  drainage  of  the  most  perfect  kind  would  not  remove 
more  than  13  per  cent  of  the  water  by  weight,  equivalent  to  3.6  per  cent  of  the  volume 
of  the  rock.  However,  most  of  the  samples  from  the  drained  rock  were  taken  very 
close  to  the  surface,  so  that  very  likely  they  lost  some  of  their  water  through  drying 
out  by  the  heat  of  the  sun,  for  the  dry  season  was  more  than  a  month  old  at  the  time 
they  were  collected. 


12  THE   PANAMA   CANAL. 

These  facts  show  that  while  the  sliding  rocks  have  a  high  percentage  of  pore  space, 
the  pores  are  mostly  of  capillary  size  and  are  filled  with  water  which  obeys  the  laws  of 
capillarity  and  which  can  not,  therefore,  be  drained  off.  These  experiments  defi- 
nitely established  that  all  ciu-es  by  drainage  which  had  been  offered  to  and  urged  on 
the  canal  authorities  were  absolutely  futile,  and  the  money  which  might  have  been 
wasted  in  worthless  tunnels,  wells,  and  acres  of  asphalt  covering,  was  saved  for  the 
only  remedy  that  could  bring  permanent  cure  under  the  circumstances — dredging. 

Before  considering  the  suggestions  tliat  have  been  made  for  con- 
trolVing  or  preventing  the  shdes  other  than  those  aheady  mentioned, 
it  may  be  well  to  state  what  was  attempted  by  the  canal  forces  in 
this  direction  prior  to  the  occurrence  of  the  slides  which  are  now 
active. 

During  the  excavation  of  the  Cut  22  slides  and  breaks  of  various 
extent  occurred.  The  steps  taken  to  protect  exposed  slopes  by  vege- 
tation have  been  noted.  It  was  believed  that  piles  driven  through 
the  loose  material  into  firm  ground  below  and  tied  at  the  tops  might 
check  the  movement,  and  this  was  tried  at  four  of  the  slides,  but 
without  success.  In  some  instances  the  piles  were  carried  bodily 
down  the  slope;  in  others  the  underlying  material,  moving  faster 
than  the  upper  portion,  inclined  the  piles  away  from  the  Cut,  and  in 
cases  where  the  top  surface  moved  faster  than  at  the  bottom,  they 
inclined  in  the  opposite  direction.  The  remains  of  these  piles  can 
be  seen  at  the  present  time  in  some  of  the  areas  so  treated. 

It  was  thought  that  in  case  of  clay  slides  heavy  riprap  dumped  on 
the  surface  would  find  its  way  through  the  loosened  material  to  firm 
ground  and  check  the  movement,  but  this  method  was  found  as  use- 
less as  the  pUing.  Most  of  the  riprap  rock  was  taken  out  at  the  foot 
of  the  slope  as  the  excavation  proceeded.  Experiments  were  made 
by  concreting  the  face  of  the  prism  to  prevent  the  disintegrating 
effect  of  the  air  on  some  of  the  softer  rocks ;  this  was  done  by  use  of  a 
cement  gun,  by  plastering  the  surface  with  cement  mortar  and  by 
reinforced  concrete,  anchored  to  the  side  of  the  prism  with  pieces  of 
rail.  None  of  these  methods  was  satisfactory  or  durable.  The  rem- 
nants of  the  French  drains,  which  proved  inadequate,  were  dug  out  at 
the  bottom  of  the  prism.  The  conclusion  was  reached  that  the  only 
cure  was  the  removal  of  all  loosened  material  as  it  came  into  the  Cut, 
and  in  case  of  breaks  to  relieve  the  weight,  where  possible,  from  the 
upper  parts  of  the  banks  by  steam  shovels  or  sluicing  operations. 

In  considering  any  method  for  stopping  the  slides  some  concep- 
tion must  be  had  of  the  enormous  amount  of  material  involved,  as 
well  as  the  method  in  which  it  acts.  The  banks  at  present  giving 
trouble  are  from  300  feet  to  approximately  550  feet  above  sea  level, 
and  extend  back  1,300  to  1,800  feet  from  the  faces  of  the  prism,  and 
from  these  farthest  points  to  the  water  surface  the  entire  mass  is 
broken  for  a  depth  extending  at  least  to  the  bottom  of  the  canal. 
As  already  explained,  the  movement  is  by  fits  and  starts,  sudden  at 


BEPOET   OF   THE   GOVERNOR.  13 

fii-st  and  gradually  subsiding,  with  renewed  activity  after  a  period 
of  quiescence.  For  instance,  in  August,  1916  a  general  movement 
occurred  at  the  east  Culebra  slide  and  consisted  of  a  settlement  from 
20  to  25  feet  vertically  down  at  the  rear  portion  of  the  area  affected, 
some  1,300  feet  from  the  prism,  by  which  a  mass  of  material  from 
the  lower  part  was  projected  into  the  Cut  beyond  the  center  line, 
reducing  the  depth  of  water  along  this  line  an  average  of  5  feet. 
Because  of  the  width  of  the  new  channel,  as  well  as  the  depth,  navi- 
gation was  not  interrupted,  but  some  idea  may  be  had  of  the  enor- 
mous amount  of  material  that  must  be  held  back  by  any  artificial 
construction  or  device  smiilar  to  those  which  have  been  proposed, 
and  the  impossibility  of  their  construction  must  be  recognized. 

Suggestions  most  frequently  made  have  been  along  the  line  of 
sowing  vegetation  and  of  properly  draining  the  area.  These  have 
aheady  been  considered.  To  sink  a  number  of  pipes  and  apply 
steam  for  drying  out  the  subsoil  would  be  prohibitive  on  the  score  of 
expense,  even  if  it  were  practicable.  It  would  be  impossible  to  drive 
and  hold  such  pipes  through  the  material  in  case  of  motion.  Pipes 
sunk  for  the  purpose  of  pumping  out  the  water  are  equally  imprac- 
ticable and  impossible.  From  the  experiments  conducted  by  Prof. 
Warren  J.  Mead  and  Mr.  MacDonald  all  the  water  could  not  be  ex- 
tracted by  this  method.  Pihng  the  entire  area  at  regular  intervals 
and  tying  the  piles  to  anchors  driven  in  the  firm  ground  can  not  be 
done,  nor  would  it  secure  the  result  anticipated  by  the  proposers  of 
this  scheme. 

The  construction  of  retaining  walls  would  require  the  excavation 
of  material  to  secure  the  foundations,  necessitating  the  removal  of 
all  the  material  in  motion,  when  the  need  for  the  retaining  wall 
would  no  longer  exist.  There  is  no  form  of  construction  that  could 
be  designed  that  would  hold  back  the  superimposed  mass  while  the 
excavation  for  the  foundations  was  in  progress.  The  construction 
of  inverts  to  hold  down  the  bottom  of  the  prism  is  impracticable  and 
impossible. 

Wire  netting  rolled  over  the  bank  and  held  in  place  by  stakes' 
would  not  prevent  the  movement,  but  would  seriously  interfere  with 
the  dredges  in  removing  the  material  littered  up  with  sections  of 
wire  mesh,  which  would  break  loose  with  every  movement  of  the 
sUde.  Consohdating  the  mass  by  injecting  grout  would  also  be 
impossible;  the  pipes  could  not  be  driven  to  firm  ground  below  and 
the  earth  and  rock,  as  it  now  comes  into  the  Cut,  can  be  much  more 
easily  handled  than  would  be  the  case  were  this  material  solidified 
by  cement. 

It  was  suggested  that  the  slopes  and  the  surface  of  the  ground  adja- 
cent to  the  Cut  be  covered  with  asphalt,  tar,  or  some  preparation 
which  would  exclude  water  from  the  ground.     This  was  also  pro- 


14  THE  PANAMA  CANAL. 

posed  by  a  member  of  the  committee  from  the  National  Academy  of 
Sciences.  That  the  committee  did  not  include  it  among  its  recom- 
mendations seems  conclusive  that  in  its  opinion  it  was  not  practicable, 
and  no  further  comment  seems  necessary. 

A  number  of  theories  have  been  advanced  as  to  the  cause  of  the 
difficulties,  among  them  that  there  exists  a  huge  reservoir  of  water 
within  the  earth  and  the  pressure  therefrom  produces  the  shdes.  If 
this  be  so,  the  pressure  being  sufficient  to  break  the  ground  would 
release  the  water  and  aUow  its  escape.  All  the  water  that  is  drained 
from  the  slide  areas  is  accounted  for  by  the  rainfaU  and  by  the  escape 
of  any  ground  water  that  the  movement  might  hberate,  and  the 
theory  is  untenable.  The  mutual  attraction  of  the  large  masses  on 
either  side  of  the  Cut  is  assigned  as  the  cause  for  bringing  down  the 
material,  and  yet  another  that  a  huge  magnet  that  previously  existed 
has  been  cut  in  two. 

The  latest  theory  advanced  appears  in  an  article  pubhshed  in  the 
New  York  Sun  on  June  18,  1916,  by  the  Hon.  Thomas  Kearns, 
ex  United  States  Senator  from  Utah,  and  repubhshed  as  Senate 
Document  No.  525,  Sixty-fourtli  Congress,  first  session. 

He  believes,  "*  *  *  that  the  trouble  is  all  caused  by  subter- 
ranean gases  formed  in  the  earth  which,  when  permitted  to  escape 
through  certain  channels  or  breaks  in  the  earth,  carry  with  them 
eruptive  material,  sometimes  for  a  long  distance,  to  the  place  of  the 
least  resistance."  Coming  from  a  man  with  such  large  practical 
experience,  it  undoubtedly  carried  conviction  to  the  minds  of  many 
who  read  it.  Since  Senator  Kearns' s  examination  was  more  thorough 
than  that  made  by  Prof.  Benjamin  Le  Roy  Miller,  Ph.  D.,  it  is  com- 
forting to  note  from  his  judgment  also  that  Gold  and  Contractors 
HiUs  are  not  likely  to  faU  into  the  Cut. 

Senator  Kearns  is  in  error  when  he  states,  ''Since  it  (the  canal)  was 
first  opened  to  navigation  on  August  14,  1914,  it  has  been  closed  and 
out  of  commission  virtually  two-thirds  of  the  time."  The  canal  was 
opened  to  traflB.c  August  15,  1914,  and  up  to  June  18,  the  date  of  the 
article,  the  canal  was  closed  232  days  out  of  656  days,  or  approx- 
imately one-third  of  the  time,  instead  of  two-thirds,  as  stated. 

Another  error  is  that  there  was  an  upheaval  in  the  bottom  of  the 
Cut  at  some  other  point  than  the  Culebra  section.  At  no  portion  of 
the  canal  has  there  been  any  upheaving  except  in  the  2,000  feet  north 
of  Gold  HiU.  This  upward  movement  first  occurred  when  the  excava- 
tion had  reached  elevation  175  feet  above  sea  level,  or  135  feet  above 
the  finished  bottom  of  the  canal.  The  upheaval,  as  the  result  of  the 
present  slides,  reached  an  elevation  of  65  feet  above  the  water  surface, 
or  110  feet  above  the  bottom  of  the  canal.  In  no  case  was  there  a 
movement  at  the  bottom  that  was  not  preceded  by  a  movement  in 
the  adjacent  bank.     The  movement  in  the  bottom  ceased  entirely  in 


EEPOET  OF   THE  GOVERNOE.  15 

1913,  when  the  side  slopes  were  made  sufficiently  flat  to  reduce  the 
pressure  exerted  by  them  to  less  than  that  required  to  accomplish 
this  upward  movement.  The  upheaving  in  the  bottom  occurred 
again  subsequent  to  the  break  in  October,  1914,  when  the  huge 
masses  of  the  banks  crowded  toward  the  axis  of  the  canal  and  dis- 
turbed the  condition  of  pressure  that  existed  prior  to  the  occurrence 
of  the  shdes.  Part  of  the  shoaling  in  the  canal  is  undoubtedly  due 
to  the  resistance  to  the  motion  of  the  mass  at  some  part  of  the  bottom, 
which  throws  part  of  the  slide  itself  upward  with  the  effect  shown. 

According  to  Senator  Kearns's  theory,  gases  forming  somewhere  in 
the  interior  of  the  earth  in  escaping  carry  with  them  eruptive  material 
to  the  place  of  least  resistance,  or  in  this  instance  through  the  bottom 
of  the  canal.  The  breaks,  which  produced  fissures  several  hundred 
feet  deep,  liberated  no  gas.  With  a  pressure  sufficient  to  accomplish 
such  destruction  of  the  structural  formation  of  the  rocks,  apparently 
the  gases  returned  to  their  storage  to  attempt  later  a  forced  passage 
through  the  bottom.  We  unconsciously  endeavored  to  assist  their 
efforts  by  digging  away  110  feet  of  their  container,  but  even  this  did 
not  induce  the  gases  to  come  forth;  thus  far  there  has  been  no  evi- 
dence of  escape  anywhere  along  the  hne  of  the  canal,  nor  has  there 
been  any  upheaving  movement  anywhere  except  in  the  Culebra 
district,  where  the  slides  occur.  So  long  as  there  is  no  movement  in 
the  banks  we  are  able  to  reach  bottom  grade  and  keep  it.  Under  the 
circumstances,  those  on  the  work  stiU  adhere  to  their  belief  that 
subterranean  gases  have  nothing  whatever  to  do  with  the  movements 
that  have  occurred. 

The  methods  proposed  for  securing  a  channel  through  the.  slides 
and  to  maintain  it,  adopted  in  October,  1915,  were  laid  before  the 
committee  of  the  National  Academy  of  Sciences,  including  the  sluicing 
operations  proposed  on  the  west  side,  but  no  suggestions  were  made 
which  modified  the  plan  in  any  way.  The  various  propositions  made 
by  a  number  of  people  seeking  to  help  us  in  our  troubles  were  care- 
fully considered,  as  were  also  the  theories  advanced  setting  forth  the 
probable  causes.  There  were  a  number  of  letters,  the  writers  pro- 
posing, for  suitable  monetary  consideration,  to  cure  the  slides,  but 
these  were  filed.  None  of  the  suggestions  or  theories  tended  in  any 
way  to  change  the  plans  adopted. 

The  dredges  did  their  work  so  well  that  a  channel  was  cut  through 
the  Isthmus  connecting  the  two  banks,  of  sufficient  size  to  pass  the 
small  ships  still  tied  up  and  awaiting  transit.  By  April  15,  1916,  a 
sufficiently  stable  channel  had  been  secured  to  warrant  opening  the 
canal  to  navigation,  and  the  transit  of  shipping  has  continued  to 
date.  Except  at  "Gibraltar"  the  waterway  is  500  feet  wide  with  40- 
foot  depth  over  the  greater  part,  this  depending  on  the  movements 
that  occur  in  the  banks.     So  far  as  the  Culebra  slides  are  concerned, 


16  THE   PANAMA   CANAL. 

the  worst  is  over;  the  intervals  between  movements  are  becoming 
greater  and  the  quantities  of  material  less;  the  only  danger  being  at 
"Gibraltar,"  but  it  is  hoped  that  the  excavation  continued  along  the 
lines  contemplated  will  enable  the  widening  of  this  section  to  the 
adopted  prism  line  without  interfering  in  any  way  with  the  transit 
of  shipping.  The  reopening  of  the  canal  was  at  the  beginning  of  the 
rainy  season,  and  thus  far  the  rainfall  has  been  above  the  normal. 

The  recent  movement  at  Cucaracha  was,  as  usual,  the  unexpected, 
coming  as  it  did  from  the  high  ground  in  the  northeast  corner  of  the 
slide  area.  The  difficulty  attending  this  was  not  a  question  of  amount 
of  material,  for  the  dredges  could  cope  easily  with  the  movement  on 
this  score;  the  hard  flinty  rock  was  difficult  to  break  up,  and  caused 
irritating  and  aggravating  delays. 

As  predicted  at  the  time  the  great  Culebra  movements  occurred, 
the  slides  will  be  overcome  finally  and  for  all  time,  notwithstanding 
the  calamity  howlers  and  in  spite  of  the  disastrous  predictions  of  the 
*' know-it-alls." 

o 


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